Enhancing Moisture and Electrochemical Stability of the Li5.5PS4.5Cl1.5 Electrolyte by Oxygen Doping

Chlorine-rich argyrodite-type solid electrolyte Li5.5PS4.5Cl1.5 has been a promising choice for solid-state batteries (SSBs) because of its ultrafast Li-ion conduction. However, the poor air/moisture stability and low electrochemical stability with pristine high-voltage cathodes hinder their applications. Herein, O-substituted Li5.5PS4.5-xOxCl1.5 (x = 0, 0.075, 0.175, and 0.25) solid electrolytes are successfully synthesized. Among them, Li5.5PS4.425O0.075Cl1.5 delivers high ionic conductivity, improved moisture resistance, and enhanced electrochemical stability in higher voltage windows. SSBs using Li5.5PS4.425O0.075Cl1.5 show higher capacities and superior cyclability than those using Li5.5PS4.5Cl1.5 combined with a pristine LiNi0.8Mn0.1Co0.1O2 cathode when operated at a high end-of-charge voltage of 4.5 V (vs Li+/Li0). Moreover, the batteries exhibit outstanding performance in a wide temperature range. This work provides a strategy to modify the inherent drawbacks of sulfide electrolytes, promoting their practical applications.